Abstract: A joint prosthesis comprises two pins each designed to be directly or indirectly inserted into a respective one of the two bones to be joined. Operative between the pins are articulation surfaces comprising, in the case of one of the pins, referred to as the carrier pin, two domes centered on an axis perpendicular to the carrier pin, oriented in opposite directions relative to each other and carried by the carrier pin. In the case of the other pin, referred to as the carried pin, the articulation surfaces comprises two further domes each complementary to a respective one of the first-mentioned domes, and thus adapted to be engaged therewith, carried by the carried pin. The domes of the carrier pin are carried by respective pegs which are movable transversely relative to the two pins, the carrier pin comprising two arms each having two respective aligned housings in which the pegs are slidably inserted.